. >> fracking has been used in the united states for decades, and it was developed quite a long time ago to do exactly what we do now with the natural gas. >> well, not exactly. frackers used to just drill straight down. >> and they've now turned the drill bit at a 90-degree angle once it's hit the bottom. >> that's called "horizontal fracking." some claim this might actually cause small earthquakes. another issue is what's being pumped into the rock to force out the gas. new mixes of sand, water and chemicals are being used. critics claim those mixes may be more dangerous. >> ♪ with names like benzene and formaldehyde ♪ ♪ you better keep it far away from the water supply ♪ >> these companies are using highly toxic and, in some cases, chemicals that are known human carcinogens, which means chemicals that cause cancer. >> some believe that fracking too close to schools is causing problems. >> in states all across this country, where kids are coming home from school after playing during recess or during after-school sports practices, complaining of severe headaches, nausea, the